F.E. Cecil

Radiative capture of protons by light nuclei at low energies

Abstract Gamma-ray-to-charged-particle branching ratios, and gamma-ray angular distributions have been measured for the radiative capture of protons by 6 Li, 7 Li, 9 Be and 11 B for proton bombarding energies between 40 and 180 keV. Except for the 163 keV resonance in the reaction 11 B(p, γ) 12 C, the branching ratios are roughly independent of energy and the angular distributions are isotropic. These measurements are used to deduce reaction S -factors and infer thermonuclear reactivities. The measurements are compared to distorted-wave-Born-approximation direct-capture cross-section calculations.

Total cross-section measurements for the production of nuclear gamma rays from light nuclei by low-energy deuterons☆

Abstract The thick target yields of the reactions 6Li, 9Be, 10B(d, nγ) for specific final nucleus γ-rays have been measured between deuteron bombarding energies of 48 and 170 keV. The measured thick target yields are used, together with recently published values of the stopping power of low-energy deuterons in matter, to infer the total reaction cross sections for the production of the specific γ-rays between deuteron energies of 65 and 160 keV. The cross sections are compared to appropriate Coulomb barrier penetration probabilities and the astrophysical functions S(E) are deduced.

Comparison of 6Li(d, n1) 7Be AND 6Li(d, p1) 7Li mirror reactions at low energies

Abstract Zero-degree thick-target yields of the isotropic γ-decay from the mirror 1 2 − states in 7 Be and 7 Li have been measured for deuteron beams on enriched 6 Li for laboratory energies from 60 to 160 keV. The 7 Be∗ to 7 Li∗ yield ratio drops from 1.05 at 160 keV to 0.94 at 60keV. This increase in the (d, p 1 ) strength is as expected if the projectile is electrically polarized as it nears the target nucleus. The measured thick-target yields over these beam energies allow a quantitative calculation of an effective energy shift due to the deuteron polarization. This is compared to the shift calculated for the theoretical value for the polarizability of the deuteron, using a cutoff DWBA method. Use of a zero-range constant D o renonnalized for polarization effects gives an energy-independent enhancement of the (d, p) cross sections at low energies.

Measurement of astrophysical S-factors for deuteron-induced reactions on 7Li, 9Be, 10B, and 11B at low energies☆

Abstract We have measured total cross sections for the reactions (d,α) and (d, αn) on 7Li between center-of-mass (c.m.) energies of 35 and 120 keV, the reactions (d,p) and (d,α) to all excited states with positive Q-values on the nuclei 9Be, 10B, and 11B between c.m. energies of 70 and 132 keV, 72 and 138 keV and 90 and 140 keV respectively and the reaction (d,t) on the nucleus 9Be to the 8Be ground state between c.m. energies of 70 and 132 keV. Astrophysical S-factors for these reactions are derived from the total cross section measurements.

The reaction 6 Li(d, nγ) 7 Be and the energy loss of low energy deuterons in matter

Thick target yields for the reaction 6Li(d, nγ)7 Be have been measured using LiF and LiCl targets at deuteron bombarding energies between 48 and 170 keV. Assuming recently published values for the stopping powers of deuterons in Li and F, the LiF thick target yields were used to deduce the total cross section for the reaction, 6Li(d, nγ)7 Be. The cross section varies from about 0.3 mb at 160 keV to about .004 mb at 60 keV. A comparison between the yields measured used the LiF and LiCl targets allowed a measurement of the relative stopping powers of deuterons in F and Cl. A significant discrepancy is observed between our measured values of the relative stopping powers and the predicted value of the relative stopping powers based on recently published values.